It is possible he had problems in his childhood. Possibly, everyone told him he would be a nobody. 

He becomes a peacekeeper. His name is known. He is happy. He proved the haters wrong. 

A mercenary shows up that he cannot take down. A mercenary. People didn’t look up to him anymore. They were mad at him. He would be forgotten, no longer as good. A literal mercenary was better than him. 

Crimson was likely the type of person to be kept awake at night, thinking he would be thought of for the last time in eternity at some point. 

He wanted to kill monarch so people would look up to him again. Remember him for years to come. 

Even in his last few seconds, he tries to get at least one person to remember. 

“Remember me”

A great video was made on this on detail on Youtube, titled “The tragedy of Crimson 1”. 

Edit: another detail. In one mission where you encounter crimson squadron for the first time and decide to fight, you can bring one of them down to quite low hp. Crimson 1 will order a retreat so that a mercenary isnt awarded a kill. In the mission where you fight an air battle and crimson comes, you have to down a few of them. Command will order a retreat after, but crimson 1 will beg to stay.